Method of constructing commutators for dynamos or motors



3 Sheets-Sheet 1 (N0 Model.)

E.THOMSON. METHOD OF CONSTRUGTING COMMUTATORS FOR DYNAMOS OR MOTORSa No. 516,845. Patented Mar. 20, 1894.

FEE

(No' Model.) 3 SheetsSheet 2.

E. THOMSON.

METHOD OF OONSTRUOTING OOMMUTAIORS FOR DYNAMOS OR MOTORS.

No. 516,845. Patented Mar. 20,1894.

FIG..B H39.

W i JV (No Model.) 3 Sheets-Sheet 3.

E. THOMSON. METHOD OF OONSTRUOTING OOMMUTATORS FOR DYNAMOS OR MOTORSF No 516,845. Patented Mar. 20, 1894,

R I R? I R FIELIEI- FIG-l4- "ml NATIONAL pmomurmm COMPANY v vummaron a c Nrrnn STATES PATENT FFICE.

ELIilU THOMSON, OF SlVAMPSCOTT, MASSACHUSETTS, ASSIGNOR TO THE THOMSON- IOUSTON ELECTRIC COMPANY, OF CONNECTICUT.

METHOD OF CONSTRUCTING COMMUTATORS FOR DYNAMOS OR MOTORS.

SFECIFICATION forming part of Letters Patent No. 516,845, dated March 20, 1894.

Application filed January 24, 1891. Serial No. 378,891. (No model.)

To (0% whom it may concern.-

Be it known that I, ELIHU THOMSON, a citizen of the United States, residing at Swampscott, in the county of Essex and State of Massachusetts, have invented a certain new and useful Improvement in Methods of Constructing Commutators for Dynamos or Motors, of which the following is a specification.

The present invention relates to a method of constructing commutators for electric motors, dynamos, or similar apparatus, and it consists in casting the metal parts of the commutator in a mold around or between the insulating division pieces or strips separating the segments. For this purpose a mold is prepared leaving a space or form in which the metal is to run when cast, and the division strips of insulating material are fixed in the mold in proper positions to form a commutator of the desired form and size when complete. I find that a suitable material for the division strips, and one which stands the heat of casting, is what may be called biscuit ware formed by baking clay at a moderate temperature, and producing a variety of earthenware material known as porous cup material or a material similar to porous cup material. It is a composition of clay tempered with a little sand and possibly a little feldspar. Other materials may sufiice for the purpose of my invention, but this one I mention particularly as I have found it satisfactory.

My improved method will be understood by reference to the accompanying drawings, wherein Figure 1 is a section of a mold as prepared for casting; Fig. 2 a detail view of one of the division strips 5 Fig. 3 a view of the mold with division strips in place; Fig. 4 a perspective view of the casting; Figs. 5 and 6 are sectional and face views of the commutator mounted upon an armature shaft. Figs. 7 to 11 inclusive are corresponding views illustrating the method of casting a cylindrical commutator, and Figs. 12, 13, and let illustrate the same method, when the holders for joining the parts of the commutator together are fixed in the mold previous to casting rather than formed by the casting process itself.

In Fig. 1, C represents the upper part of a mold as prepared for casting consisting of sand or loam rammed into the cope, and N is the lower half of the mold, between which is left the space K formed by a pattern, in which the metal is to run during the casting process.

The mode of procedure is more clearly shown in Fig. 3. Here the division pieces I, consisting of thin strips of biscuit ware or porous cup ware shaped as shown in Fig. 2, are placed in the mold with spaces between them for the reception of the molten metal, which will preferably be of copper or copper slightly alloyed to assist its fluidity and soundness in casting. The division pieces are held in place by holders R, R placed in the mold which, as hereinafter described bind the parts of the commutator together, while it is being turned down or otherwise finished after casting. It is essential that the division pieces be firmly held, to resist the tendency to displacement when flooded with the molten metal. The holders R, R are rings of metal, adapted to receive and rigidly support the strips I. The segments, when cast, become welded to the holders, so that the product is a rigid article, which can be handled without danger of its falling apart. The gates used in the casting operation are seen at G, G. The holders may also be cast around the commutator, and for this purpose a space would be formed in the mold as seen at Z, Fig. 1. IVhen the casting is taken from the mold it is as seen in Fig. i, where G, G are the metal pieces formed by the gates or vents, K, K K 850., are the metal segments of the commutator, I the division strips, and R R the holders or rings whereby the segments are not allowed to come apart or drop their insulating septums during the mechanical operations of finishing the commutator. The casting in Fig. t makes what may be called a disk commutator, that is, one in which the metal segments are in the form of a disk secured near its cen ter. It is trued by putting it on an arbor and turning on a lathe in the usual way. \Vhen finished, it maybe mounted on the armature shaft, as in Fig. 5, where J is a sleeve over which the commutator is slipped, and J a binding ring or follower secured by a clamplug nut S. The parts J, J fit into V-shaped depressions in the commutator whereby the parts are held in place during revolution, and

a layer of insulating material, seen in black' to form spaces in the mold for the ring holding in-of the metal.

ers which as before explained are to be cast solid around the commutator. The rest of the pattern takes approximately the form of the finished commutator. This pattern is set up in a mold rammed in the ordinary way, and when withdrawn leaves the mold as represented in Fig. 8, where the depressions P, 1 formed by the ridges P, P, on the pattern are ready for the reception of the insulating strips which are set into the mold, as shown in Fig. 9,and the whole is ready for the pour- The casting produced willofcourse correspond in shape to the patternin Fig. 7-. It will then be turned and finished as before, and the rings will preferably be=allowed to remain until the very last.

In Fig. 11 the commutator is shown complete and mounted on an armature shaft by taper sleeves, or in any other suitable mannerwhich may be preferred by the constructer. In Figs.12to 14 an arrangementis illustrated in which the annular holders are not cast on the commutator, but are placed in the mold with the insulation strips, and serve to hold the latter in place during the casting operation. Here a pattern is constructed as in Fig. 12, and rings of metal are set into it as at R, R, R These rings form prints in the mold and the prints are afterward filled by metal rings prior to casting, as in Fig. 13. To assist in holding the insulating strips I in place, the rings are slitted or otherwise shaped so asto receive and secure the strips. This avoids difficulty in setting the pieces of insulating material in place, and the copper rings do not injure the casting operation, but Weld themselves in with the molten metal, and bind the ,same together. At the same time they have sufficient rigidity and heat resisting power to preserve the insulating material in place at the time of casting, if the operation is done properly. In Fig. 14 a casting thus produced is shown, and the subsequent processes of turning, fitting, &c., will be the same as illustrated in the preceding .figures.

By my invention I avoid some of the many difficulties in commutator construction, which are largely occasioned by the requirement of adurable insulation between the segments. The ordinary way of constructing commutators is to make the segments separately and fit them together one by one with intervening insulation. This requires very careful workmanship, but by my invention this labor is rendered unnecessary and the Whole matter reduced to extreme simplicity. The fluid metal gives the form of the parts required with the insulation in place. Indeed I find in many cases there is a strong adhesion between the cast metal and the insulating strips. The strips must of course be selected of such a character that they will not crack or sliver by the heat of molding or when the hot metal strikes them.

The process to be successful requires a pcculiar kaolin ware or biscuit ware, and the mold and the kaolin strips must be dry, to prevent filaments of copper from short-circuiting the segments. The addition to the kaolin clay of a little sand, feldspar, mica, or the like serves to produce a ware, when baked at a moderate temperature, which is not liable to crack under the heat of the molten metal.

The method is'of course applicable to dif-' ferentforms and dispositions of the commutator portions of electric apparatus, and I do not limit myself therefore to those described which show the structure as employed with dynamos or motors.

What I claim as new, and desire to secure by Letters Patent, is-- g 1. The method of constructing commutators, which consists in arranging the insulating division strips in a mold with holders by which they are held mechanically in positions corresponding to the desired form of commutator, casting the metal of the commutator around or between said division strips, finishing the commutator and removing the holders before or after the remainder of the finishing process.

2. The method of constructing commutators, which consists in placing in a mold concentric metal rings or holders, arranging radial division strips of insulating material between said holders whereby they are rigidly I held in position, casting the metal of the commutators between said division strips, and removing said holders during the finishing process, substantially as set forth.

3. The method of constructing commutators, which consists in casting copper or an alloy of copper around or between insulating division strips of earthenware material, as set forth.

4. A commutator consisting of cast metal segments, and earthenware insulation separating the segments.

5. A commutator consisting of cast metal segments separated by strips of porous kaolin ware, substantially as described.

6. A commutator consisting of cast metal segments separated by strips of biscuit ware composedof kaolin mixed with toughening materials, substantially as described.

In testimony whereof I have hereto set my hand this 20th day of January, 1891.

ELIHU THOMSON.

Witnesses: 

